Electrical relay



May 2, 1939. N. c. SHAW ELECTRICAL RELAY Filed Dec. 30, 1937 2Sheets-Sheet l N U BSR HIS ATTORNEY May 2 1939. N. c. SHAW ELECTRICALRELAY 2 Sheets-Sheet 2 Filed Dec. 30, 1937 INVENTOR [V0 C1 Ska w Y E N RO T T A m Patented May 2, 1939 UNITED STATES PATENT OFFICE ELECTRICALRELAY Noble 0. Shaw,

Penn Township,

Allegheny of Pennsylvania Application December 30, 1937, Serial No.182,501

15 Claims.

My invention relates to electrical relays, and particularly to relayswhich are adapted for flashing danger signals on highway-railroadcrossings upon the approach of a train.

More particularly, my present invention relates to flasher relays of thetype described and claimed in an application for Letters Patent of theUnited States, Serial No. 182,506, filed by A. W. Fisher and B.Mishelevich, on December 30, 1937, for Electrical relays, and one objectof my invention is to provide an improved relay of this type.

Other objects and characteristic features of my invention will appear asthe description proceeds.

I shall describe two forms of relays embodying my invention, and shallthen point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a view partly in end elevationand partly in section showing one form of relay embodying my invention.Fig. 2 is a view partly in front elevation and partly in section of therelay shown in Fig. 1. Fig. 3 is a top plan view of the relayillustrated in Fig. 1. Fig. 4 is a top plan view with the top plateremoved of the relay illustrated in Fig. 1. Figs. 5 and 6 are detailviews of parts of the relay shown in the preceding views. Fig. '7 is afragmentary end view showing a modification of a portion of the relayillustrated in Figs. 1, 2, 3 and 4.

Similar reference characters refer to similar parts in each of theseveral views.

Referring to the drawings, the reference character A designates aninsulating top plate, which top plate supports all of the operatingparts of the relay. Suspended from the top plate A by means of hangers lis a cast rectangular frame 2, and journaled at its ends in ballbearings 3 mounted in bearing cups 3a secured to the frame 2 by means ofbearing caps 20. is a rockshaft 4. This rockshaft is biased to oneposition by a compound pendulum P, and is arranged to be oscillated at apredetermined frequency which depends upon the proportioning andadjustment of the parts, by means of a suitable motor device M which Ishall describe presently. The bearing cups 3a are preferably constructedin such manner that the bearing opening is eccentric with respect to theoutside surface of the cup for a purpose which will appear hereinafter,and are provided with spring washers 6 which enclose and protect theball bearings from dirt.

The compound pendulum P may have any suitable form, but in the form hereshown, this pendulum comprises a cast U-shaped bracket 1 the upwardlyextending arms la of which are pinned to the rockshaft 4 intermediatetheir ends, and are provided at their upper ends with enlarged portionslb to provide the desired mass. A threaded post 1c is secured at itsupper end within a boss 1d formed on the underside of the yoke 1c of thebracket 1, and this post carries a counterweight 1] which is mountedeccentrically with respect to the post, and which serves both as a meansfor regulating the period of oscillation of the rockshaft within certainlimits, and also as a means for varying the position to which therockshaft is biased by means of the pendulum. The counterweight If isarranged to be locked in an adjusted position by means of nuts To whichare screwed onto the post lc on opposite sides of the counterweight.

The previously referred to motor device M for oscillating the rockshaft4 comprises an armature 8 which is pinned to the rockshaft, at one sideof the bracket 1, and an electromagnet which 00- operates with thearmature 8. This electromagnet may have any preferred construction, butin the form here shown, this electromagnet comprises a winding 9 mountedon a backstrap H) secured to the short arms Ila of L-shaped pole piecesII, the long arms Nb of which extend upwardly past the opposite sides ofthe armature 8 and are secured to depending lugs 21) formed on the frame2. One lead 9a of the winding 9 is connected to a terminal post 30mounted on the top plate A, and the other lead 9?) is connected to aconnecting post 32 which is also mounted on the top plate A. The angulardisposition of the armature 8 with respect to the rockshaft 4 is suchthat, when the rockshaft occupies the position to which it is biased bythe pendulum P, the

longer axis of the armature will be inclined at an acute angle with themagnetic field which is set up between the pole pieces II when thewinding 9 is energized. This acute angle may be varied betweenrelatively large limits, but I have found that the best operatingcharacteristics are obtained for most conditions of operation when thisangle is approximately The relay also comprises a plurality of contacts,here shown as six in number and designated by the reference charactersI2, I 3, I 4, l5, l6 and II, respectively. These contacts are of thewell-known mercury type, and each comprises a pair of electrodes I8 andI9 disposed in an evacuated or gas filled bulb containing a quantity ofmercury 20 which flows into or out of engagement with the electrodes tomake or break a circuit passing through the electrodes. The contacts l2,l 3 and M1 are mounted in spring clips 2!, 22 and 23, respectively,which are secured to the lower side of the yoke 'le of the bracket 1 asviewed in Fig. l, by means of bolts 24, and the contacts is, it and iiare mounted in spring clips 25, 2S and 2t, respectively, which aresecured to the other side of the yoke lie of the bracket 'i' by means ofthe bolts 26 in such manner that the contacts l2 and 65, the contacts I3and i5, and the contacts l4 and H are directly opposite each other.

The two contacts l2 and 85 together control the supply of energy to thewinding 9 of the motor device M, and to this end the two electrodes isof these contacts are connected together by a jumper ll, while the otherelectrodes is of these contacts are connected respectively, by means offlexible connectors 12 and t3 and conducting strips @201. and GM, to aterminal post 3! mounted on the top plate, and to the previouslydescribed connecting post 32. A source of electromotive force, hereshown as a battery Ml is connected with the terminal posts 36 and Sithrough a switch It will thus be apparent that if the switch 45 isclosed, winding 9 will be supplied with current when the contacts l2 andi5 are both closed, but that when either one of these contacts becomesopened due to the motion of the rockshaft, the supply of current to thewinding 9 will be interrupted. The position of the rockshaft at whichthe contacts iii and l5 are adjusted to open will depend upon theangular position of the armature with respect to the rockshaft and theproportioning of the parts, but when the armature is secured to therockshaft in the position shown, the contact l2 will preferably be soadjusted that it will break the operating circuit when the rockshaftswings approximately 7 in a clockwise direction, as viewed in Fig. 1,from the position to which it is biased by the pendulum, while thecontact i5 will preferably be adjusted so that it will break theoperating circuit when the rockshaft swings approximately 10 in acounterclockwise direction as viewed in Fig. 1 from the posi tion towhich it is biased by the pendulum P. It should be particularly pointedout, however, that satisfactory operation of the relay can be obtainedwith a variation of several degrees in either direction from the abovedescribed adjustment of the contacts.

The remaining contacts l3, l4, l6 and ll may be 'used for controllingthe flashing light of a highway crossing signal or any other signalingdevice, and are so adjusted that when the rockshaft i occupies theposition to which it is biased by the pendulum P, these contacts willall be open, but that oscillation of the rockshaft through its intendedamplitude will cause these contacts to become alternately opened andclosed. To facilitate making electrical connections with these contacts,the two electrodes IQ of the contacts l3 and it are connected togetherby a jumper Q8, and are also connected to a terminal post 3 i mounted onthe top plate A, by means of a flexible connector t"! and a conductingstrip did, while the remaining electrodes [8 of these contacts areconnected by means of flexible conductors 4S and and conducting strips48a and Mia to terminal posts 35 and 33, respectively, mounted on thetop plate A. In a similar manner, the two electrodes l8 of the contacts54 and ll are connected together by a jumper 59 and to a terminal post3'5 mounted on the top plate A by means of a flexible connector 5| and aconductingstrip 5w, while the electrodes [9 of these latter contacts areconnected by means of flexible conductors 52 and 53 and conductingstrips 52a and 53a to terminal posts 38 and 36 mounted on the top plateA.

It is desirable in order to minimize the stresses in thefiexible-conductors and the amount of torque required to flex them thatthese conductors should flex as little and as uniformly throughout theirlengths as possible, and to this end I provide means for clamping theconductors adjacent their lower ends in positions close to therockshaft. As here shown, these means comprise an insulating member 55(see Fig. 5) which straddles the rockshaft t between the arms la of thebracket 1, and which is secured at its ends by means of machine screws56 to inwardly extending lugs 'lh provided on the arms la. The member 55is provided in its opposite sides with spaced notches ill which receivethe flexible conductors 62, Q3, 58, 49, 4'5, M, 52 and 53, and withstuds 58 and 59 by means of which clamping members fill (see Fig. 6)having projections 6011 which extend into the notches and grip theconductors are secured to the opposite sides of the member 55. Thesemeans also comprise insulating strips provided with holes through whichthe conductors extend, and which strips control both the manner in whichthe con-- ductors flex and the spacing between the conductors. It shouldbe noted that the members 55 and til in addition to controlling themanner of flexing of the flexible conductors serve further as a meansfor preventing these members from coming into contact with any of themetal parts of the relay, thereby eliminating the possibility of shortcircuits.

Two metal stops 62 are secured to the opposite sides of the frame 2directly opposite the one arm Id of the bracket 7, and these stopscooperate with the enlarged portion lb of this arm to limit the extremeposition to which the rockshaft 4 is free to rotate.

With the relay constructed in the manner thus far described, when theswitch ie-5 is open, as shown in the drawings, so that the winding 9 ofthe electromagnet is deenergized, the rockshaft d will occupy theposition to which it is biased by the pendulum P, and under theseconditions the contacts l2 and Iii will be closed, but the contacts l3,it, it and El will all be open. When, however, the switch 45 is closed,current will flow from battery i through switch 45, terminal post 31?,lead wire 91.! of winding 9, winding 53, lead wire 9b, connecting post32, conducting strip eta, flexible connector 43, contact l5, jumper ll,contact 52, flexible connector 42, conducting strip 42a, and terminalpost 3! back to battery M. The current in winding 9 will, of course, setup a magnetic field between the pole pieces H of the electromagnet,which field will cause the armature to turn in a clockwise direction asviewed in Fig. l in order to assume a position of minimum reluctance.This rotation of the armature will, of course, be transmitted to therockshaft, and as soon as the rockshaft has been rotated to the positionin which the contact i2 opens, winding 9 will become deenergized andwill thus remove the torque tending to rotate the armature, but theshaft and armature will continue their motion beyond this position dueto the momentum of the parts. After this momentum of the parts has beenspent, however, the shaft will start to rotate in the opposite directiondue to the action of gravity on the pendulum, and as soon as thependulum returns to the position in which the contact 12 becomes closed,winding 9 will again become energized and will cause a retarding forceto be exerted on the armature. This retarding force will be small,however, because the air gaps between the pole pieces and the armaturewill then be increasing rapidly, and also because as soon as thearmature has rotated to the position in which the contact I 5 opens,winding 9 will again become deenergized. As a result, the rockshaft willswing in a counterclockwise direction to a position which is displacedfrom the position to which it is biased by the pendulum only a fewdegrees less than the previous clockwise displacement. As soon as theenergy of the rotating parts has been spent in the counterclockwisedirection, the action of gravity on the pendulum will cause a clockwisetorque to be again exerted on the shaft, and as soon as the shaft isrotated in a clockwise direction to the position in which contact l5closes, winding 9 will again become energized and will subsequentlyremain energized until therockshaft is swung to the position in whichthe contact I2 opens. The energization of winding 9 will cause a pulseof energy to be exerted on the rockshaft which assists the clockwiserotation of the rockshaft, and the parts are so proportioned that thispulse at normal operating voltages will be sufficient to supply to therockshaft the loss of energy during each cycle caused by friction, andthe retarding force of the magnet during the previous counterclockwiserotation of the rockshaft. It follows, therefore, that when switch 45 isclosed the rockshaft will oscillate at substantially the natural periodof the pendulum. This oscillation will cause the contacts l3, I4, I6 andI! to alternately open and close in an obvious manner.

The alternate opening and closing of the contacts l3, l4, l6 and I! maybe utilized for controlling the fiashing lights of a highway crossingsignal of the well-known type or for any other desired purpose. When thecontacts are used to control the flashing lights of a highway crossingsignal, it is sometimes desirable to effect the alternate flashing ofthe lights by alternately short circuiting the lamps, and when this isthe case, it is preferable that the lamp control contacts l3, I4, I 6and I! should be so arranged that when the relay is deenergized, thelamp contacts on one side of the rockshaft will be closed while those onthe other side of the rockshaft will be open, but that when the relay isoperating, there will not be any time during each oscillation of therockshaft when the lamp contacts on both sides of the rockshaft aresimultaneously closed. This result can be obtained by adjusting thecontacts unsymmetrically with respect to the pendulum biased position ofthe rockshaft, but I have found that when the contacts are adjusted inthis manner, the unsymmetrical contact adjustment tends to produce somedifference in the timing of the contacts on opposite sides of therockshaft. It is desirable that the timing of the contacts on oppositesides of the rockshaft should be uniform, and in accordance with oneform of my present invention, I accomplish even contact timing and causethe contacts to be closed on one side of the rockshaft when the relay isdeenergized without interfering with the symmetrical adjustment of thecontacts as described hereinbefor'e', by means which I shall nowdescribe.

As here illustrated, these means comprise a permanent magnet 63 which isadjustably supported above the armature 8 in such a position that whenthe relay is deenergized, this magnet will produce a counterclockwisetorque, as viewed in Fig. 1, on the armature, of such magnitude thatthis torque will rotate the rockshaft 4 away from the position to whichit is biased by the pendulum P just far enough to cause the contacts l3and I4 to become closed. The permanent magnet may be supported in thedesired position in any desired manner, but, as here shown, it isclamped to the underside of a supporting plate 64 of non-magnetizablematerial such as brass, by means of a non-magnetic clamping plate 65,and a plurality of screws 56. The screws 66 extend through spacedclearance holes provided in the clamping plate and are screwed intotapped holes 61 formed in the supporting plate.

At its opposite ends, the clamping plate 64 is provided with slottedlugs 68 which receive vertical supporting posts 69 with some clearance,and screwed onto the posts 69 on opposite sides of the lugs 68 are nuts10 by means of which the clamping plate may be secured in differentvertical positions with respect to the armature. The lower ends of theposts 69 are screwed through tapped holes provided in the enlarged headsof horizontally extending bolts H, and these latter bolts, in turn, areadjustably screwed through tapped holes provided in two of the hangersI, and are locked in adjusted positions by means of jam nuts 72.

I have found that when the permanent magnet is adjusted to produce thenecessary torque to hold the contacts l3 and I4 closed when the relay isdeenergized, it tends to balance the bias produced by the motor M whenthe relay is in operation, and that this balance is such that a strokeof practically the same length in either direction from the position towhich the rockshaft is biased by the pendulum P alone, results, thusproducing even contact timing. I have also found that under ordinaryconditions the permanent magnet has only a very small effect on thespeed of operation of therelay, there being a slight decrease in speedwhich decrease can be readily compensated for by adjusting thecounterweight 7].

Referring now to Fig. '7, I have here shown a means which may beemployed to obtain even contact timing when an unsymmetrical contactadjustment is employed to cause the contacts on one side of therockshaft to be closed and those on the other side of the rockshaft tobe open in the deenergized position of the relay. This means, in theembodiment illustrated, com-- prises a spring which is arranged toresist counterclockwise movement of the armature, as viewed in Fig. 1,from the position to which it is biased by the pendulum P. This springis secured at one end to a threaded post 16 which is adjustably mountedin a support 11 secured by means of bolts 18 to the upper end of the onepole piece I l of the motor device M, and this spring cooperates at itsinner end with an arm 19 secured to the armature. The spring is soadjusted that it will engage the arm 19 when the armature has rotated ashort distance, for example 2 or 3, in a counterclockwise direction fromthe position to which it is biased by the pendulum P, and the contacts13 and I4 are so adjusted that these contacts will be closed and thecontacts I6 and I! will be open, when the armature occupies its pendulumbiased position. The spring tends to shorten the stroke of the rockshaftin a counterclockwise direction, as viewed in Fig. 1, and it stores upenergy which is given up to the armature in. the subsequent clockwisemovement, thereby aiding the magnetic pull to produce a longer strokefrom the deenergized position in this direction.

While I have shown the spring as a coil spring, it may be made in anyconvenient form as desired, and with or without a stop for initialpressure, depending upon the operating characteristics desired.

The operating mechanism of the relay may all be enclosed within asuitable casing 88 which in the form here shown is a box-like metalcasting, three of the sides of which are provided with glass windows 8!through which the operating mechanism may be viewed. The casing is heldin position against the underside of the top plate by means of screws 82which pass through clearance holes provided in the bottom of the casing,and are screwed into tapped holes provided in the lower ends 01"depending legs 83, the upper ends of which are secured to the undersideof the frame 2.

It should be pointed out that a relay embodying my invention can be madeto oscillate without the use of the contact 15, but that this contactmaterially aids in controlling the stroke of the pendulum, and therebyinsures smooth operation of the relay. This is due to the fact that thiscontact is closed over a rather wide angle of displacement of the shaftfrom its biased position, and this contact therefore maintains thecontrol circuit closed through a longer portion of the total time ofeach operation, and in the proper section of the stroke, than would bepossible with only one control contact, which fact helps in giving asatisfactorily long stroke, and in easing up the stroke in eachdirection. The armature passes through the energized position at agreater speed at higher voltages, and there is some cornpensation due tothe contact l6 tending to limit the total stroke, although, of course,there is an increase in the length of the stroke in all cases withincreases in voltage.

It should also be pointed out that since the bearing cups are eccentric,by rotating these bearing cups the rockshaft 4 can be moved laterally topositions in which the armature is properly centered between the polepieces i I, thus providing an adjustment to take care of minorvariations in manufacture.

It should still further be pointed out that the adjustment of theposition of the operating contacts i2 and i is very important from thestandpoint of emcient power consumption and proper and eflicientoperation of the relay. The importance of the adjustment and arrangementof these contacts can be readily understood from the fact that startingvoltage, pendulum stroke, power consumption, uniformity of timing anduniformity of swing, etc. depends upon this adjustment and arrangement.

One advantage of a relay embodying my invention is that the contacts arecapable of carrying large current over a very large number of operationsof the relay without deterioration or without material change inresistance.

Another advantage of a relay embodying my invention is that the contactsare uniformly operated thus providing uniform flashing of the lightsignals controlled by the relay.

A further advantage of a relay embodying my invention is that inasmuchas there are no parts subject to impact the life of the relay isexceptionally long.

Although I have herein shown and described only two forms of electricalrelays embodying my invention, it is understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. A relay comprising a rockshaft, a pendulum secured to said rockshaft,means for at times oscillating said rockshaft at substantially thenatural period of said pendulum, a contact operated by the oscillationof said rockshaft and adjusted to occupy one position when saidrockshait occupies the position to which it is biased by said pendulum,and magnetic means for exerting a force on said rockshaft which isefiective when said rockshaft is not oscillating to rotate saidrockshaft to a position in which said contact occupies another position.

2. A relay comprising a rockshaft, a pendulum secured to said rockshaft,a first contact controlled in accordance with the position of saidrockshaft, electromagnetic means controlled by said contact foroscillating said rockshaft at substantially the natural period of saidpendulum, a second contact controlled by said rockshaft and arranged tooccupy one position when said rockshaft occupies the position to whichit is biased by said pendulum, and magnetic means for exerting a forceon said rockshaft which is effective when said rockshait is notoscillating to rotate said rockshaft to a position in which said secondcontact occupies another position but which is ineifective when saidrockshaft is oscillating to materially change its period of oscillation.

3. A relay comprising a rockshaft, a pendulum secured to said rockshaft,a first contact operated by said rockshaft, an armature secured to saidrockshaft, an electromagnet cooperating with said armature andcontrolled by said first contact for oscillating said rockshaft atsubstantially the natural period of said pendulum, magnetic meanseffective when said electromagnet is deenergized for exerting a force onsaid rockshaft which moves said rockshaft away from the position towhich it is biased by said pendulum, and other contacts controlled bythe oscillation of said rockshaft.

4. A relay comprising a rockshaft, a pendulum secured to said rockshaft,means for at times oscillating said rockshaft at substantially thenatural period of said pendulum, means effective when said rockshaft isnot oscillating for exerting a force on said rockshaft which moves saidrockshaft away from the position to which it is biased by said pendulum,and. contacts controlled by said rockshaft.

5. A relay comprising a rockshaft, a pendulum secured to said rockshaft,means for at times oscillating said rockshaft at substantially thenatural period of said pendulum, means effective when said rockshaft isnot oscillating for exerting a force on said rockshaft which moves saidrockshaft away from the position to which it is biased by said pendulum,and a contact operated by said rockshait and adjusted to occupy oneposition when said rockshaft occupies the position to which it is biasedby said pendulum and another position when said rockshaft occupies theposition to which it is moved by said second mentioned means.

6. A relay comprising a rockshaft, a pendulum secured to said rockshaft,means for at times oscillating said rockshaft at substantially thenatural period of said pendulum, means effective when said rockshaft isnot oscillating for exerting a force on said rockshaft which moves saidrockshaft away from the position to which it is biased by said pendulum,and a contact operated by said rockshaft in such manner that saidcontact will become alternately opened and closed for substantiallyuniform time intervals when said rockshaft is oscillating but will beopen when said rockshaft occupies the position to which it is biased bysaid pendulum and will be closed when said rockshaft occupies theposition to which it is moved by said means.

7. A relay comprising a rocksha-ft, a pendulum secured to saidrockshaft, a first contact operated by said rockshaft, an armaturesecured to said rockshaft, an electromagnet cooperating with saidarmature and controlled by said first contact for oscillating saidrockshaft at substantially the natural period of said pendulum, magneticmeans eifective when said electromagnet is deenergized for exerting aforce on said rockshaft which moves said rockshaft away from theposition to which it is biased by said pendulum, and other contactscontrolled by said rockshaft in such manner that said contacts will bealternately opened and closed for substantially equal time intervalswhen said rockshaft is oscillating but that some of said contacts willbe closed and others opened when said electromagnet is deenergized.

8. A relay comprising a rockshaft, a pendulum, means for oscillatingsaid rockshaft at substantially the natural period of said pendulum,contacts controlled by said rocks'haft and arranged in such manner thatsaid contacts will become alternately opened and. closed when saidrockshaft is oscillating but that some of said contacts will be closedand others opened when said rockshaft occupies the position to which itis biased by said pendulum, and means for con trolling the distance saidrockshaft rotates in both directions from the position to which it isbiased by said pendulum to cause said contacts to become alternatelyopened and closed for substantially equal time intervals.

9. A relay comprising a rockshaft, a pendulum secured to said rockshaft,a first contact operated by said rockshaft, an armature secured to saidrockshaft, an electromagnet cooperating with said armature andcontrolled by said first contact for oscillating said rockshait atsubstantially the natural period of said pendulum, a second magnetassociated with said armature and effective when said electromagnet isdeenergized for exerting a force on said rockshaft which moves saidrockshaft away from the position to which it is biased by said pendulum,and other contacts controlled by said rockshaft.

10. A relay comprising a rockshaft, a pendulum secured to saidrockshaft, a first contact operated by said rockshaft, an armaturesecured to said rockshaft, an electromagnet cooperating with saidarmature and controlled by said first contact for oscillating saidrocks'haft at substantially the natural period of said pendulum, apermanent magnet associated with said armature and effective when saidelectromagnet is deenergized for exerting a force on said rockshaftwhich moves said rockshaft away from the position to which it is biasedby said pendulum, and other contacts controlled by said rockshaft.

11. A relay comprising an electromagnet provided with pole pieces, amovable armature mounted to rotate between said pole pieces, a pendulumoperatively connected with said armature, a permanent magnet associatedwith said armature and effective when said electromagnet is deenergizedfor exerting a force on said armature which moves said pendulum awayfrom its gravity biased position, a first tube secured to said pendulum,fiuid means within said tube adapted when the pendulum is swung to oneposition to close a circuit for said magnet and when the tube is swungto another position to open the circuit for said magnet, and a secondtube carried by said pendulum and containing a pair of electrodes and afluid which flows into and out of engagement with said electrodes toalternately open and close a contact in response to swinging movement ofsaid pendulum between two extreme positions, said second tube beingsecured to said pendulum in such a position that said fluid will notengage said electrodes when said pendulum occupies its gravity biasedposition but will engage said electrodes when it is moved away from itsgravity biased position by said permanent magnet.

12. A relay comprising an electromagnet provided with pole pieces, amovable armature mounted to rotate between said pole pieces, a pendulumoperatively connected with said armature, a permanent magnet associatedwith said armature and efiective when said electromagnet is deenergizedfor exerting a force on said armature which moves said pendulum awayfrom its gravity biased position, means for energizing saidelectromagnet in a manner to cause said pendulum to oscillate atsubstantially its natural period, and a tube carried by said pendulumand containing a pair of electrodes and a fluid which alternately flowsinto and out of engagement with said electrodes in response tooscillation of said pendulum, said tube being secured to said pendulumin such a position that said fluid will not engage said electrodes whensaid pendulum occupies its gravity biased position but will engage saidelectrodes when it is moved away from its gravity biased position bysaid permanent magnet.

13. A relay comprising an electromagnet provided with pole pieces, amovable armature mounted to rotate between said pole pieces, a pendulumoperatively connected with said armature, means for energizing saidelectromagnet in a manner to cause said pendulum to oscillate atsubstantially its natural period, a pair of mercury contacts secured tosaid pendulum on opposite sides of its: pivotal axis and adjusted toboth be open when said pendulum occupies its gravity biased position,and a permanent magnet associated with said armature and eifective whensaid electromagnet is deenergized to exert a force on said armaturewhich rotates it away from its gravity biased position to a position inwhich one of said contacts becomes closed.

14. A relay comprising an electromagnet provided with pole pieces, amovable armature mounted to rotate between said pole pieces, a pendulumoperatively connected with said armature, means for energizing saidelectromagnet in a manner to cause said pendulum to oscillate atsubstantially its natural period, mercury contacts secured to saidpendulum on opposite sides of its pivotal axis and adjusted in suchmanner that one of said contacts will be open and the other will beclosed when said pendulum occupies its gravity biased position, andspring means cooperating with said pendulum to resist rotation of saidpendulum in the direction to close the normally closed contact.

15. A relay comprising an electromagnet provided with pole pieces, amovable armature mounted to rotate between said pole pieces, a pendulumoperatively connected with said armature, means for energizing saidelectromagnet in a manner to cause said pendulum to oscillate atsubstantially its natural period, contacts secured to said pendulum onopposite sides of its pivotal axis and adjusted in such manner that oneof said contacts is open and the other is closed when said pendulumoccupies its gravity biased position, and spring means cooperating withsaid pendulum to shorten its stroke in one direction and lengthen it inthe other to cause said two contacts to become alternately opened andclosed for substantially equal time intervals when said 10 pendulum isoscillating.

NOBLE C. SHAW.

